Expectant mothers will get child benefit during the last months of their pregnancy as part of a package of measures designed to help the government meet its target of halving child poverty by 2010.

Gordon Brown said the benefit would be paid to all mothers-to-be from the 29th week of pregnancy. But the change will not come in until April 2009, so it will not help women who are pregnant now or about to begin a family.

The chancellor resisted calls from anti-poverty campaigners for families to be given the same level of child benefit for all their children. Child benefit is the universal benefit paid to families with children, regardless of income. From April 2007, weekly rates go up to £18.10 - a 65p rise - for the eldest or only child, and to £12.10 - up 40p - for each other child.

The chancellor told the Commons: "I have received powerful representations that in the last months of pregnancy, when nutrition is most important, and in the first weeks after birth, the extra costs borne by parents could be better recognised if we did more to help through our universal benefit." Maternity grants were currently available to low-income expectant mothers from the 29th week of pregnancy, but from April 2009, help would be available to all during the latter stages of pregnancy.

Official documents say the change will make mothers-to-be "up to £200 better off". This is based on an average pregnancy lasting 40 weeks, and is made up of 11 lots of £18.10. But some medical experts say a typical full-term pregnancy really lasts 38 weeks. And a woman having her second or third child would typically be about £130 better off.

The chancellor also announced that from April, the value of the child element of child tax credit would increase by £80 to £1,845 a year. In the 2007-08 tax year, a family with two children and a full-time earner on £16,500 a year will receive more than £110 per week in child tax credit and child benefit - more than double the equivalent support given in 1997-98, the government said.

The Child Poverty Action Group said the extension of child benefit to unborn children "will be a tremendous boost to parents preparing for the birth of their child". A spokeswoman added: "It will help the poorest children get a better start in life as their parents will be better resourced to provide the care they need from the day they are born."

But the group was disappointed that Mr Brown did not extend the higher rate of child benefit to subsequent children.

Tax credits have come under increasing fire from campaigners. One Parent Families joined the Child Poverty Action Group and Citizens Advice yesterday in voicing concerns that the tax credit regime was losing its effectiveness in raising living standards.

The One Parent Families chief executive, Chris Pond, said: "We welcome the uprating of child tax credit with earnings, fulfilling the promise [in this year's budget], but as a member of the campaign to end child poverty we believe the chancellor must invest a further £4bn to halve child poverty by 2010."

While child tax credit and working tax credit have lifted the incomes of millions of families, if those on low pay try to increase their earnings, they are held back by a combination of taxes and loss of benefits equal to a 73p income tax rate. The combination of tax payments and the withdrawal of benefits acts as a disincentive to earn more and raise living standards further.

Mr Pond said the government needed to act quickly to maintain the momentum of recent years. He said single parents on income support should be allowed to keep all of any child maintenance they got from the Child Support Agency or its successor.

"This single measure would, at a stroke, remove a further 90,000 children from poverty and give the government a far better chance of reaching its 2010 target of halving child poverty."

Other measures

Personal allowances to rise in line with inflation. Allowance of £5,035 will rise by £190 to £5,225 in April. For those aged 65 to 74 it rises from £7,280 to £7,550.

National insurance limits to increase in line with inflation. No change in rates for employers and employees. Lower earnings limit rises to £87 - up £3 - and upper limit by £25 to £670 from April. Self-employed Class-2 contributions rise to £2.20 a week. Annual lower profits limit for Class-4 contributions will increase in line with inflation to £5,225.

Tax credits Basic element of working tax credit rises to £1,730 in April. Disabled worker element increases to £2,310. No change to childcare element of working tax credit. The child element of the child tax credit rises from £1,765 to £1,845, although the income threshold and income disregard levels are unchanged.

Life insurance "Pension term assurance" - life policies with relief on premiums - to end as it is seen as a tax loophole.

Pensions Alternatively secured pensions will have higher tax charges to deter all but the scheme's target - the Plymouth Brethren - from applying. ASPs may be withdrawn if there is continued misuse.

Financial advice Financial inclusion fund to get extra £2.5m to recruit and train more advisers to help the indebted. The extra funding will take the number of advisers to 500.

Shopping overseas Tax-free allowance for travellers coming from outside the EU doubles to £290 from next year.